DC Cooling Fan - neat way to run 'em

[fdesalvo]

There is an abundance of easily found info on how to run your DC fan using the PT's filament supply.  What I didn't know is that the vast majority of these DC powered fans have internal rectifiers, negating the need to regulate the the PT's filament juice.  

The info I'm linking to states you can connect your fan directly to the 6.3v supply without fear.  If your fan has no/slow movement, a cap and diode may be added.  Here's a really neat way to do this:

http://www.blueglow.de/FenFan.html

Here's what I bought - 80mm

[Tyrannocaster]

Neat idea and nice info page. Thanks.

[Ed_Chambley]

Weber sells a little mod kit with a 2 speed switch.  $15.00.  Got one in every amp I have.  I don't direct the fan at the tubes tho.  I mount them at the preamp end just to get circulation.

[fdesalvo]

Just trying to pay it forward 

I've seen Weber's kits and they look like a great solution, as well.  He's like a reputable version of Dan Torres. 

[The_Gaz]

I did not know about most DC fans having internal rectification. How would one determine if their fan had an internal rectifier? Simply just try and run it off AC?

[PRR]

> DC fans having internal rectification

I would not put it that way. Most are one transistor and one resistor, two coils (trigger and power).

However I can see that for typical voltages (under 7V, perhaps a bit more), in reverse, nothing happens. So it runs slower, but OK.

And perhaps some makers are adding full-wave rectifiers to avoid problems with customers who don't know which way is which?

[The_Gaz]

> DC fans having internal rectification

I would not put it that way. Most are one transistor and one resistor, two coils (trigger and power).

However I can see that for typical voltages (under 7V, perhaps a bit more), in reverse, nothing happens. So it runs slower, but OK.

And perhaps some makers are adding full-wave rectifiers to avoid problems with customers who don't know which way is which?

I am definitely one of those customers that doesn't know which way is which. Am I wrong in thinking that there is no wrong way to hook them up across the heaters? PRR, do you recommend a rectifier off the heaters even i the fan run directly off the AC heater winding?

My heaters are also elevated to 70vdc. on the CT. That shouldn't matter should it?

[The_Gaz]

bump!

[fdesalvo]

I bult the lil' rectifier circuit according to the link above and it works really well!  The fan is damn near silent, but I wonder if it's output is enough to effectively cool things down.  I guess all the amp needs is a little circulation. 

[schoolie]

Very nice, fdesalvo!  What do you think about venting the chassis?  I'm thinking of installing the fan in a cutout of the back panel, above the PT.  I'm more concerned about my filter caps than the tubes.  Also, do you think it makes sense to install an inline 100mA fuse with the rectifier?  I wonder if this fan could take out the heater circuit if it failed.

Thanks for the link!

[fdesalvo]

I honestly don't think it's worth fusing the fan - it draws such little current!  Even if your chassis is hanging upide down, the chances of thetubes/PT cooking the caps is really slim.  My chassis sits upright, Marshall style and the cab will have a long vent across the top.  I'm going to position the fan where it's mounted in the cab itself to help move some air around the tubes/PT- not exactly sure where yet.  Will have to wait for the cab to arrive.

Very nice, fdesalvo!  What do you think about venting the chassis?  I'm thinking of installing the fan in a cutout of the back panel, above the PT.  I'm more concerned about my filter caps than the tubes.  Also, do you think it makes sense to install an inline 100mA fuse with the rectifier?  I wonder if this fan could take out the heater circuit if it failed.

Thanks for the link!

[schoolie]

I guess you're right about the fan fuse, as long as it doesn't short.  I notice my chassis gets pretty hot, so I taped a thermocouple to my filter caps and the temp hit 110F after fifteen minutes of playing.  I regret placing them above the tube sockets now, but a fan inside or outside the chassis would help.

Thanks!

Rob

[fdesalvo]

Don't go inside chassis- dust can be conductive.

[schoolie]

Don't go inside chassis- dust can be conductive.

Outside it is, then.
  Thanks

[fdesalvo]

Sho nuff